Grain sorghum, a traditional crop in the Coastal Bend of Texas is usually planted early in the spring. In fact, in many years we are planting by the end of February, but this year we have been delayed by much needed rainfall. When considering planting dates, note that too early planting with potentially cool air and soil temperatures can needlessly retard growth while delayed plantings will risk sorghum midge potential and flowering/maturation under hotter conditions with reduced rainfall in July and August.
If the average soil temperature has not reached a five-day average of at least 60 F at two inch depth, consider delaying planting. An ideal temperature for quick germination and establishment of grain sorghum is near 65 F. The minimum soil temperature at the desired planting depth for germination and emergence of sorghum is about 55 F, but expect slow growth.
Another very important decision that is made by sorghum growers is hybrid selection. The initial criteria most producers make in choosing a grain sorghum hybrid in Texas is maturity. Once an appropriate maturity range is decided upon, then yield is paramount. Full-season, and even medium-long, maturity hybrids in South and Central Texas (unless irrigated in the Lower Rio Grande or Coastal Bend) can exhaust available moisture before maturity, and thus have reduced yields potential especially in dry years. There are several sources for hybrid test information including your local County Extension Agent (Nueces County - http://nueces.agrilife.org/publications/grain-sorghum-result-demonstrations/), Texas AgriLife Research Crop Testing Program, found on the web at; http://varietytesting.tamu.edu/and various seed companies. In addition to maturity and yield, other hybrid parameters such as tillering, lodging, weathering, stay-green, head exsertion, grain color, panicle type, disease resistance and herbicide tolerance could have a potentially major impact on sorghum performance in Texas. Take tillering for example; Hybrids express differences in tillering. Note that early planting and low populations foster increased tillering. Although tillering is one important means by which sorghum hybrids may adapt to their environment,high tillering hybrids where drought stress is expected could be problem. In contrast, low tillering hybrids reduce the possibility that early favorable conditions lead to increased tillering, only to have drought and heat increase, leaving the plant with too little moisture per head hence reducing actual yield.
In drought years the lodging or standability factor could be important. Drought stress and limited moisture conditions can lead to charcoal and other stalk rots which cause lodging, especially when plant populations are high. Gulf Coast wind and storm damage can also make strong standing sorghum hybrids more valuable.
Selecting sorghum seed based on price alone is a poor choice. Low-priced seed probably does not represent the best yield potential and proven genetics you would like to have for your farm. Shop hybrid maturity and yield potential, scour the yield trial data, narrow your choices, then find your best price for those hybrids on your short-list, and don’t fret paying $2-3 per acre more to plant the hybrid of your choice.
Planting rates should be done on planting seeds per acre rather than pounds per acre. Grain sorghum seed can vary widely in seed size, often 12,000 to 18,000 seeds per pound with 13,000 to 16,000 being most common. Lower seeding rates can produce higher yields when droughty conditions prevail and you are begging for a rain. Lower plant populations are suited to these drought conditions preserving more moisture per individual plant, thus reducing the plant’s stress level. Moisture and yield potential is conserved as less moisture is used to produce unneeded stems and leaves while the crop is better able to wait extra days until that next rain you are hoping for. Furthermore,anywhere in Texas, high plant populations for the production environment, will enhance the development of charcoal and other stalk rots in drought-stressed plants, leading to lower yield and significant lodging potential. Reduced seeding rate is perhaps the key for managing grain sorghum production risk anywhere in Texas, unless you have full control of irrigation. Depending upon soil moisture conditions, recommended seeding rates vary between 30,000 and 80,000 plants per acre for South Texas. Don’t be too quick to assume that your production conditions merit the highest end of this range. Under limited moisture conditions, 2 to 4 plants per foot for 38-inch row spacings will normally use all available soil moisture.
Row spacing is another issue to consider. Grain sorghum can be planted in a wide range of row spacing from 6 to 40-inch rows. Depending on the area predominant row spacing is 30 inch, 36 inch, 38 inch or 40 inch rows. A few producers use 15 inch or 20 inch rows on occasion by either drilling or using an interplant planter. Research in San Patricio County and Temple shows increased yields with 30 inch row spacing versus wider rows. Making rows 30 inches instead of 38 to 40 inches can help shade the soil faster and reduce weed growth.
More information and on sorghum production can be found at http://www.sorghumcheckoff.com/sorghum-production-handbooks
